Diamine compound having dendron side chain and liquid crystal alignment material produced using the same

ABSTRACT

Disclosed herein are a novel diamine compound having a dendron side chain and a liquid crystal alignment material produced using the diamine compound. Specifically, the diamine compound is used to prepare a polyamic acid, which is then used to produce the liquid crystal alignment material. According to the liquid crystal alignment material, the pretilt angle of a liquid crystal is easy to control, and the alignment properties of a liquid crystal are good. Particularly, since the liquid crystal alignment material shows superior chemical resistance to washing solvents used in LCD panel fabrication processes, it has an advantage in that the alignment properties of a liquid crystal are not degraded even after washing.

TECHNICAL FIELD

The present invention relates to a diamine compound having a dendronside chain, and a liquid crystal (LC) alignment material produced usingthe diamine compound. More particularly, the present invention relatesto a technique for providing an LC alignment material by introducing adendron side chain into a diamine compound wherein the pretilt angle ofa liquid crystal is easy to control, the alignment properties of aliquid crystal are good, and the chemical resistance of the alignmentmaterial during washing is superior.

BACKGROUND ART

In general, conventional polyimide resins for liquid crystal alignmentfilms are prepared from the polycondensation of an aromatic dianhydride,e.g., pyromellitic dianhydride (PMDA) or biphthalic dianhydride (BPDA),and an aromatic diamine, e.g, para-phenylenediamine (p-PDA),meta-phenylenediamine (m-PDA), 4,4-methylenedianiline (MDA),2,2-bisaminophenylhexafluoropropane (HFDA),meta-bisaminophenoxydiphenylsulfone (m-BAPS),para-bisaminophenoxydiphenylsulfone (p-BAPS),4,4-bisaminophenoxyphenylpropane (BAPP) or4,4-bisaminophenoxyphenylhexafluoropropane (HF-BAPP), as monomers.

DISCLOSURE Technical Problem

Polyimide liquid crystal alignment films produced from the aromaticdianhydrides and the diamines are superior in thermal stability,chemical resistance, mechanical properties, and the like. However, thepolyimide liquid crystal alignment films have problems of poortransparency and solubility due to the formation of a charge transfercomplex, and poor electrooptical properties. In efforts to solve theseproblems, Japanese Patent Laid-open No. Hei 11-84391 describes theintroduction of an alicyclic dianhydride monomer or an alicyclicdiamine, and Japanese Patent Laid-open No. Hei 06-136122 discloses theintroduction of a functional diamine having a side chain or a functionaldianhydride having a side chain in order to increase the pretilt angleof a liquid crystal and improve the stability of a liquid crystal.Further, a vertical alignment type alignment film was developed thatenables liquid crystal molecules to be aligned vertically to the surfaceof the film to constitute an LCD panel in a vertical alignment (VA) mode(see, U.S. Pat. No. 5,420,233).

As the market for liquid crystal display devices has recently expanded,there is a continuing demand for high-quality display devices. Further,as technologies for large-area liquid crystal display devices have maderemarkable progress, there exists a strong need to produce an alignmentfilm with high productivity. Thus, there is a continuing need in the artto develop a high-performance liquid crystal alignment film capable ofsufficiently meeting different characteristics, e.g., few defects in LCDfabrication processes, excellent electrooptical properties, and highreliability, required in various liquid crystal display devices.

[Technical Solution]

The present inventors have earnestly and intensively conducted researchto solve the above-mentioned problems of the prior art. As a result, thepresent inventors have found that a liquid crystal alignment materialproduced using a functional diamine with a dendron side chain enableseasy control of pretilt angle and uniform alignment of a liquid crystal,and shows superior chemical resistance during washing, thusaccomplishing the present invention.

Specifically, in accordance with one aspect of the present invention,there is provided a diamine compound represented by Formula 1 below:

wherein

A is a single bond, —O—, —COO—, —CONH—, or —OCO—;

B is a single bond, —O—, —COO—, —CONH—, or —OCO—;

the substituents C are independently a single bond, —O—, —COO—, —CONH—,or —OCO—; and

the substituents D are independently a C₁₋₂₀ linear, branched or cyclicalkyl group which may be substituted with at least one halogen atom, ora functional group represented by Formula 2 below:

wherein the substituents C′ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D′ are independently a C₁₋₂₀ linear, branched or cyclicalkyl group, or a functional group represented by Formula 3 below:

wherein the substituents C″ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D″ are independently a C₁₋₂₀ linear, branched or cyclicalkyl group, or a functional group represented by Formula 4 below:

wherein the substituents C′″ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D′″ are independently a C₁₋₂₀ linear, branched orcyclic alkyl group.

In accordance with another aspect of the present invention, there isprovided a polyamic acid prepared by copolymerizing the diaminecompound, an alicyclic dianhydride, an aromatic cyclic dianhydride, andoptionally, an aromatic cyclic diamine and/or a siloxane-based diamine.

In accordance with another aspect of the present invention, there isprovided a soluble polyimide prepared by wholly or partially imidizingthe polyamic acid.

In accordance with another aspect of the present invention, there isprovided a mixture of the polyamic acid and the soluble polyimide.

In accordance with another aspect of the present invention, there isprovided a liquid crystal alignment film produced by dissolving thepolyamic acid, the soluble polyimide, or the mixture thereof in asolvent, coating the solution on a substrate, and wholly or partiallyimidizing the coated solution.

In accordance with yet another aspect of the present invention, there isprovided a liquid crystal display device comprising the liquid crystalalignment film.

Hereinafter, the present invention will be explained in detail.

The present invention provides a functional diamine represented byFormula 1 below:

wherein

A is a single bond, —O—, —COO—, —CONH—, or —OCO—;

B is a single bond, —O—, —COO—, —CONH—, or —OCO—;

the substituents C are independently a single bond, —O—, —COO—, —CONH—,or —OCO—; and

the substituents D are independently a C₁₋₂₀ linear, branched or cyclicalkyl group which may be substituted with at least one halogen atom, ora functional group represented by Formula 2 below:

wherein the substituents C′ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D′ are independently a C₁₋₂₀ linear, branched or cyclicalkyl group, or a functional group represented by Formula 3 below:

wherein the substituents C″ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D″ are independently a C₁₋₂₀ linear, branched or cyclicalkyl group, or a functional group represented by Formula 4 below:

wherein the substituents C′″ are independently —O—, —COO—, —CONH—, or—OCO—; and

the substituents D′″ are independently a C₁₋₂₀ linear, branched orcyclic alkyl group.

Specific examples of the functional diamine compound include compoundsrepresented by Formulae 5 and 6 below:

However, the compounds of Formulae 5 and 6 are provided for illustrativepurposes only, and the structure of the functional diamine according tothe present invention is not limited thereto.

Since the functional diamine monomer of the present invention has abenzene ring skeleton, acting as a spacer, in its side chain, lesssteric hindrance is caused. Accordingly, this structural effectminimizes a decrease in the reactivity of the diamine monomer, assistsin the alignment of liquid crystal molecules in the direction of theside chain, and improves the chemical resistance of an alignment film tobe produced, thus greatly contributing to an improvement in theresistance to washing. In addition, since a plurality of alkyl groupscan be simultaneously introduced into the side chain to form a dendronstructure, even a low content of the diamine monomer results in anincreased pretilt angle. These characteristics of the functional diaminemonomer stabilize the pretilt angle of a liquid crystal, and alignliquid crystal molecules in a direction perpendicular to the surface ofa alignment film to be produced.

The present invention provides a polyamic acid prepared bycopolymerizing the functional diamine having a dendron side chain, analicyclic dianhydride, an aromatic cyclic dianhydride, and optionally,an aromatic cyclic diamine and/or a siloxane-based diamine.

The polyamic acid can be prepared from the acid dianhydride and thediamine compound by conventional copolymerization processes. Thesecopolymerization processes are not particularly limited so long as theycan be used to prepare polyamic acids. Since the polyamic acid containsthe functional diamine unit, the pretilt angle of a liquid crystal iseasy to control and the alignment of a liquid crystal becomes uniform.Since the pretilt angle is varied according to the content of thefunctional diamine monomer, the polyamic acid can be prepared by usingthe functional diamine alone without the use of the aromatic cyclicdiamine or the siloxane-based diamine, depending on the mode of liquidcrystal displays. Thereafter, the polyamic acid thus prepared can beused to produce a liquid crystal alignment film. That is, the aromaticdiamine or the siloxane-based diamine is an optional component.Accordingly, the content of the functional diamine of Formula 1 in thepolyamic acid is in the range of 0.1˜100 mole %, preferably 0.5 mole %to 30 mole %, and more preferably 1 mole % to 20 mole %, relative to thetotal amount of the diamine monomers.

Examples of suitable aromatic cyclic diamines used for the preparationof the polyamic acid include, but are not limited to,para-phenylenediamine (p-PDA), 4,4-methylenedianiline (MDA),4,4-oxydianiline (ODA), meta-bisaminophenoxydiphenylsulfone (m-BAPS),para-bisaminophenoxydiphenylsulfone (p-BAPS),2,2-bisaminophenoxyphenylpropane (BAPP), and2,2-bisaminophenoxyphenylhexafluoropropane (HF-BAPP).

The siloxane-based diamine used for the preparation of the polyamic acidaccording to the present invention has a structure represented byFormula 7 below:

Formula 7

wherein n is an integer of from 1 to 10.

The amount of the aromatic cyclic diamine and/or the siloxane-baseddiamine used is in the range of 0˜99.9 mole %, preferably 70˜99.5 mole%, and more preferably 80˜99 mole %, based on the total amount of thediamine monomers.

The aromatic cyclic dianhydride used for the preparation of the polyamicacid according to the present invention causes an alignment film havinga thickness of about 0.1 μm to be resistant to a rubbing process, whichis carried out in order to align liquid crystal molecules in onedirection, to be heat resistant to high temperature processing processesat 200° C. or above, and to be resistant to chemicals.

Examples of such aromatic cyclic dianhydrides include, but are notlimited to, pyromellitic dianhydride (PMDA), biphthalic dianhydride(BPDA), oxydiphthalic dianhydride (ODPA), benzophenonetetracarboxylicdianhydride (BTDA), and hexafluoroisopropylidene diphthalic dianhydride(6-FDA).

The content of the aromatic cyclic dianhydride is between 10 mole % and95 mole %, and preferably between 50 mole % and 90 mole %, relative tothe total amount of the dianhydride monomers. If the aromatic cyclicdianhydride is used in an amount of less than 10 mole %, an alignmentfilm to be produced is poor in mechanical properties and heatresistance. On the other hand, if the aromatic cyclic dianhydride isused in an amount exceeding 80 mole %, the electrical properties, e.g.,voltage holding rate, are worsened.

The alicyclic dianhydride used for the preparation of the polyamic acidaccording to the present invention solves problems, for example,insolubility in common organic solvents, low transmittance in thevisible light region due to the formation of a charge transfer complex,poor electrooptical properties due to high polarity, resulting from themolecular structure of the polyamic acid, etc.

Examples of the alicyclic dianhydride include, but are not limited to,5-(2,5-dioxotetrahydrofuryl)-3-methylcyclohexene-1,2-dicarboxylicdianhydride (DOCDA), bicyclooctene-2,3,5,6-tetracarboxylic dianhydride(BODA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA),1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), and1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA).

The content of the alicyclic dianhydride is between 5 mole % and 90 mole%, and preferably between 10 and 50 mole %, based on the total amount ofthe dianhydride monomers.

The polyamic acid of the present invention is highly soluble in generalaprotic polar solvents, e.g., N-methyl-2-pyrrolidone (NMP),γ-butyrolactone (GBL), dimethylformamide (DMF), dimethylacetamide(DMAc), and tetrahydrofuran (THF). It is believed that the superiorsolubility of the polyamic acid is largely attributed to theintroduction of the alicyclic dianhydride and the steric effects of thefunctional diamine present in a three-dimensional structure due to largesteric repulsion between the three benzene rings in view of themolecular structure of the functional diamine. As liquid crystal displaydevices have recently become large-scale, high resolution and highquality, the printability of alignment materials has been gainingimportance. Under these circumstances, good solubility has a positiveinfluence on the printability on a substrate when the functional diamineis used to produce liquid crystal alignment films.

The polyamic acid of the present invention preferably has anumber-average molecular weight of 10,000 to 500,000 g/mol. When thepolyamic acid is imidized, it has a glass transition temperature of 200°C. to 350° C. depending on the imidization rate or the structure of thepolyamic acid.

The present invention provides a liquid crystal alignment film producedby dissolving the polyamic acid in a solvent, coating the solution on asubstrate, and wholly or partially imidizing the coated solution.

Alternatively, the liquid crystal alignment film of the presentinvention can be produced from a soluble polyimide alone, which isprepared by wholly or partially imidizing the polyamic acid, or amixture of the polyamic acid and the soluble polyimide.

The alignment film shows a transmittance of 90% or higher in the visiblelight region, uniform alignment of a liquid crystal, and easy control ofthe pretilt angle of a liquid crystal within the range of 1°˜90°. Inaddition, since the alignment film contains the functional diamine, itshows improved electrooptical properties, e.g., low refractive index andlow dielectric constant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in more detail withreference to the following examples. However, these examples are givenfor the purpose of illustration and are not to be construed as limitingthe scope of the invention.

PREPARATIVE EXAMPLE 1 (1) Preparation of 3,4,5-tris(n-dodecyloxy)benzoylchloride

One mole of (1) was dissolved in DMF in a round-bottom flask equippedwith a condenser, and then 3.9 moles of potassium carbonate was addedthereto. The resulting mixture was sufficiently stirred. After 3.1 molesof (2) was added to the stirred mixture, the reaction temperature of theflask was slowly raised to 70° C. Thereafter, the reaction mixture wasallowed to react for 24 hours while maintaining the temperature at 80°C. After the reaction was completed, the temperature was dropped to roomtemperature. The reacted solution was poured into pure water to form aprecipitate. The precipitate was filtered, and washed several times toobtain a clean product (3). The product (3) was dissolved in ethanol,and then potassium hydroxide was added thereto. The ethanolic solutionwas refluxed for 4 hours to obtain an acid derivative (4). The acidderivative (4) was subjected to acylation by refluxing it for 4 hourstogether with thionyl chloride, to give 3,4,4-trisdodecyloxybenzoylchloride (5).

(2) Preparation of 12G1-AG-terphenyldiamine

One mole of dibromobenzoic acid (6) was charged in a sufficiently driedround-bottom flask, and then THF was added thereto to dissolve the acid(6). After DCC and DMAP were added to the solution, the temperature ofthe flask was cooled to 0° C. While 1.1 moles of aminophenol was slowlyadded to the cooled solution, the reaction mixture was reacted for 30minutes to form an intermediate (8). The intermediate (8) was dissolvedin THF, and TEA as a catalyst was added thereto. To the solution wasadded the compound (5). The resulting mixture was reacted at roomtemperature for 3 hours to obtain an intermediate (9). Next, moistureand oxygen present inside a sufficiently washed and dried round-bottomflask were removed in vacuo, and instead, the flask was filled withargon (Ar) as an inert gas. The intermediate (9) was charged into theflask, and then DME was added thereto to dissolve the intermediate (9).Palladium phosphate and sodium carbonate as catalysts were added to thesolution, and then 2.2 mole equivalents of aminoboronic acid (10) wasadded thereto. After the resulting mixture was homogeneously dissolved,the temperature of the flask was raised to 80° C. The solution wasallowed to react for 24 hours while maintaining the temperature at 80°C. After completion of the reaction, the reaction solution was purifiedby column chromatography and recrystallization to give the final product12G1-AG-terphenyldiamine.

The structure of the final product was identified through ¹H-NMRspectrum, and thermal characteristics were evaluated using differentialscanning calorimetry (DSC). The results are shown in FIGS. 1 and 2,respectively.

EXAMPLE 1

0.99 moles of 4,4-methylenedianiline and 0.01 moles of12G1-AG-terphenyldiamine (dendron diamine, Formula 5) were charged intoa four-neck flask equipped with a stirrer, a thermostat, a nitrogeninjection apparatus and a condenser while passing nitrogen through theflask, and then N-methyl-2-pyrrolidone (NMP) was added thereto. Theresulting mixture was dissolved. To the solution was added 0.5 moles of5-(2,5-dioxotetrahydrofuryl)-3-methylcyclohexane-1,2-dicarboxylicanhydride (DOCDA) in a solid state, and 0.5 moles of pyromelliticdianhydride (PMDA). The resulting mixture was vigorously stirred. Atthis time, the solid content was 15% by weight. While maintaining at atemperature lower than 25° C., the reaction mixture was allowed to reactfor 24 hours to prepare a polyamic acid solution.

To evaluate the chemical resistance of the alignment films, the polyamicacid solution was spin coated on ITO glass substrates (10 cm×10 cm) to athickness of 0.1 μm, cured at 70° C. and 210° C., and rubbed to producealignment films. Thereafter, the surface of the alignment films wassufficiently washed with isopropyl alcohol and pure water, and then thealignment films were assembled to fabricate an LCD test cell. While theLCD test cell was driven by applying a voltage of 1˜2V thereto, theformation of stains on the LCD test cell was observed. The results areshown in Table 1.

Further, to evaluate the alignment properties and measure the pretiltangle of a liquid crystal by rubbing, the polyamic acid solution wasapplied to two ITO glass substrates to a thickness of 0.1 μm, and curedat 210° C. to produce two alignment films. At this time, thespreadability and curling properties at the ends of the alignment filmwere observed visually or using an optical microscope to evaluate theprintability of the alignment film. On the other hand, the surface ofthe alignment films were rubbed using a rubbing machine, the alignmentfilms were arranged parallel to each other in such a manner that therubbing direction of one alignment film was opposed to that of the otheralignment film, and the two alignment films were sealed to fabricate aliquid crystal cell having a cell gap of 50 μm. After the liquid crystalcell was filled with liquid crystal molecules, the alignment propertiesof the liquid crystal were observed under an orthogonally polarizedoptical microscope, and the pretilt angle of the liquid crystal wasmeasured by a crystal rotation method. The results are shown in Table 1.

EXAMPLE 2

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.98 moles of 4,4-methylenedianiline and 0.02 moles of12G1-AG-terphenyldiamine were used. In accordance with the proceduresdescribed in Example 1, the alignment properties of the liquid crystalwere evaluated, the pretilt angle of the liquid crystal was measured,and the chemical resistance of the alignment film was evaluated. Theresults are shown in Table 1.

EXAMPLE 3

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.95 moles of 4,4-methylenedianiline and 0.05 moles of12G1-AG-terphenyldiamine were used. In accordance with the proceduresdescribed in Example 1, the alignment properties of the liquid crystalwere evaluated, the pretilt angle of the liquid crystal was measured,and the chemical resistance of the alignment film was evaluated. Theresults are shown in Table 1.

EXAMPLE 4

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.92 moles of 4,4-methylenedianiline and 0.08 moles of12G1-AG-terphenyldiamine were used. In accordance with the proceduresdescribed in Example 1, the alignment properties of the liquid crystalwere evaluated, the pretilt angle of the liquid crystal was measured,and the chemical resistance of the alignment film was evaluated. Theresults are shown in Table 1.

EXAMPLE 5

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.85 moles of 4,4-methylenedianiline- and 0.15 moles of12G1-AG-terphenyldiamine were used. In accordance with the proceduresdescribed in Example 1, the alignment properties of the liquid crystalwere evaluated, the pretilt angle of the liquid crystal was measured,and the chemical resistance of the alignment film was evaluated. Theresults are shown in Table 1.

COMPARATIVE EXAMPLE 1

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.9 moles of 4,4-methylenedianiline and 0.1 moles of2,4-diaminophenoxyhexadecane were used. In accordance with theprocedures described in Example 1, the alignment properties of theliquid crystal were evaluated, the pretilt angle of the liquid crystalwas measured, and the chemical resistance of the alignment film wasevaluated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2

A polyamic acid was prepared in the same manner as in Example 1, exceptthat 0.85 moles of 4,4-methylenedianiline and 0.15 moles of2,4-diaminophenoxyhexadecane were used. In accordance with theprocedures described in Example 1, the alignment properties of theliquid crystal were evaluated, the pretilt angle of the liquid crystalwas measured, and the chemical resistance of the alignment film wasevaluated. The results are shown in Table 1.

TABLE 1 Vertical Chemical Example No. Pretilt angle (°) Printabilityalignment resistance Example 1 3.6 Good No Good Example 2 7.1 Good NoGood Example 3 79.0 Good Weak Good Example 4 =89 Good Good Good Example5 =89 Good Good Good Comparative 6.7 Good No Poor Example 1 Comparative12.7 Weak No Poor Example 2[Advantageous Effects]

As apparent from the above description, the present invention provides aliquid crystal alignment material wherein the alignment properties of aliquid crystal are good, the pretilt angle of a liquid crystal is easyto control, and the chemical resistance of the alignment material duringwashing is superior.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

DESCRIPTION OF DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a ¹H-NMR spectrum of a diamine compound prepared inPreparative Example 1 of the present invention; and

FIG. 2 is a differential scanning calorimetry (DSC) thermogram of adiamine compound prepared in Preparative Example 1 of the presentinvention.

1. A diamine compound represented by Formula 1 below:

wherein A is a single bond, —O—, —COO—, —CONH—, or —OCO—; B is a singlebond, —O—, —COO—, —CONH—, or —OCO—; the substituents C are independentlya single bond, —O—, —COO—, —CONH—, or —OCO—; and the substituents D areindependently a C₁₋₂₀ linear, branched or cyclic alkyl group which maybe substituted with at least one halogen atom, or a functional grouprepresented by Formula 2 below:

wherein the substituents C′ are independently —O—, —COO—, —CONH—, or—OCO—; and the substituents D′ are independently a C₁₋₂₀ linear,branched or cyclic alkyl group, or a functional group represented byFormula 3 below:

wherein the substituents C″ are independently —O—, —COO—, —CONH—, or—OCO—; and the substituents D″ are independently a C₁₋₂₀ liner, branchedor cyclic alkyl group, or a functional group represented by Formula 4below:

wherein the substituents C″′ are independently —O—, —COO—, —CONH—, or—OCO—; and the substituents D″′ are independently a C₁₋₂₀ linear,branched or cyclic alkyl group.
 2. The diamine compound according toclaim 1, wherein the diamine compound is a compound represented byFormula 5 or 6 below:


3. A polyamic acid prepared by copolymerizing the diamine compoundaccording to claim 1, an alicyclic dianhydride, an aromatic cyclicdianhydride, and optionally, an aromatic cyclic diamine and/or asiloxane-based diamine.
 4. The polyamic acid according to claim 3,wherein the diamine compound according to claim 1 is present in anamount of 0.1˜100 mole %, and the aromatic cyclic diamine and thesiloxane-based diamine are present in an amount of 0˜99.9 mole %, basedon the total amount of the diamine monomers.
 5. The polyamic acidaccording to claim 3, wherein the aromatic cyclic dianhydride is presentin an amount of 10˜95 mole %, and the alicyclic dianhydride is presentin an amount of 5˜90 mole %, based on the total amount of thedianhydride monomers.
 6. The polyamic acid according to claim 3, whereinthe polyamic acid has a number-average molecular weight of 10,000 to500,000 g/mol.
 7. A soluble polyimide prepared by wholly or partiallyimidizing the polyamic acid according to claim
 3. 8. A mixture of thepolyamic acid according to claim 3 and the soluble polyimide accordingto claim
 7. 9. A liquid crystal alignment film produced by dissolvingthe polyamic acid according to claim 3, the soluble polyimide accordingto claim 7 or the mixture according to claim 8 in a solvent, coating thesolution on a substrate, end wholly or partially imidizing the coatedsolution.
 10. A liquid crystal display device comprising the liquidcrystal alignment film according to claim 9.